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Biomedical subjects

R A Bates

Publications and source records attributed to R A Bates.

14 recordsLinked to original sources
PubMed2006

National survey of the technique of intravitreal triamcinolone injection in the United Kingdom.

OBJECTIVES: Intravitreal injection of steroids is a rapidly evolving treatment option for a variety of retinal pathologies. There is wide variation among ophthalmologists regarding dose of steroid and the technique of injection. Through this survey we aim to describe the current practice of injection of intravitreal steroid among ophthalmic consultants in the United Kingdom and review the literature. METHODS: A postal questionnaire was sent to all the 901 ophthalmic consultants in the United Kingdom. The questions covered frequency of intravitreal steroid injections, subspecialty interest, dosage and volume of steroid, patient preparation, surgeon preparation, and postoperative management. RESULTS: The response rate to the questionnaire was 63%. A total of 24.7% perform intravitreal steroid injections regularly with 90% of users performing five or fewer injections per month. In all, 94% use a dose of 4 mg. Among surgeons, 38% do not prescribe postoperative antibiotics or steroids and 59% check intraocular pressure either on the same or the next day. CONCLUSION: The relatively short experience with this technique has not yet allowed a clear picture to emerge of indications, complications or best practice administration. Published descriptions of intravitreal steroid injection techniques vary widely and variations are not evidence based. Observed UK practice is diverse.

Anterior Chamber↗
PubMed1999

Evaluation of frequency and time-frequency spectral analysis of heart rate variability as a diagnostic marker of the sleep apnoea syndrome.

The sleep apnoea/hypopnoea syndrome (SAHS) elicits a unique heart rate rhythm that may provide the basis for an effective screening tool. The study uses the receiver operator characteristic (ROC) to assess the diagnostic potential of spectral analysis of heart rate variability (HRV) using two methods, the discrete Fourier transform (DFT) and the discrete harmonic wavelet transform (DHWT). These two methods are compared over different sleep stages and spectral frequency bands. The HRV results are subsequently compared with those of the current screening method of oximetry. For both the DFT and the DHWT, the most diagnostically accurate frequency range for HRV spectral power calculations is found to be 0.019-0.036 Hz (denoted by AB2). Using AB2, 15 min sections of non-REM sleep data in 40 subjects produce ROC areas, for the DFT, DHWT and oximetry, of 0.94, 0.97 and 0.67, respectively. In REM sleep, ROC areas are 0.78, 0.79 and 0.71, respectively. In non-REM sleep, spectral analysis of HRV appears to be a significantly better indicator of the SAHS than the current screening method of oximetry, and, in REM sleep, it is comparable with oximetry. The advantage of the DHWT over the DFT is that it produces a greater time resolution and is computationally more efficient. The DHWT does not require the precondition of stationarity or interpolation of raw HRV data.

Adult↗
PubMed1998

2-deoxy-D-glucose-induced metabolic stress enhances resistance to Listeria monocytogenes infection in mice.

Exposure to different forms of psychological and physiological stress can elicit a host stress response, which alters normal parameters of neuroendocrine homeostasis. The present study evaluated the influence of the metabolic stressor 2-deoxy-D-glucose (2-DG; a glucose analog, which when administered to rodents, induces acute periods of metabolic stress) on the capacity of mice to resist infection with the facultative intracellular bacterial pathogen Listeria monocytogenes. Female BDF1 mice were injected with 2-DG (500 mg/kg b. wt.) once every 48 h prior to, concurrent with, or after the onset of a sublethal dose of virulent L. monocytogenes. Kinetics of bacterial growth in mice were not altered if 2-DG was applied concurrently or after the start of the infection. In contrast, mice exposed to 2-DG prior to infection demonstrated an enhanced resistance to the listeria challenge. The enhanced bacterial clearance in vivo could not be explained by 2-DG exerting a toxic effect on the listeria, based on the results of two experiments. First, 2-DG did not inhibit listeria replication in trypticase soy broth. Second, replication of L. monocytogenes was not inhibited in bone marrow-derived macrophage cultures exposed to 2-DG. Production of neopterin and lysozyme, indicators of macrophage activation, were enhanced following exposure to 2-DG, which correlated with the increased resistance to L. monocytogenes. These results support the contention that the host response to 2-DG-induced metabolic stress can influence the capacity of the immune system to resist infection by certain classes of microbial pathogens.

Adjuvants, Immunologic↗
PubMed1998

Nonlinear pharmacokinetics of tissue-type plasminogen activator in three animal species: a comparison of mathematical models.

A recent study presented plasma concentrations of tissue-type plasminogen activator in three different animal species and at several different dose levels. A three-compartment mammillary model with capacity-limited elimination (of Michaelis-Menten form) was postulated to describe the data. In the present study, several alternative model structures are examined with the view of determining whether better fits can be obtained, whether linear models are significantly worse than nonlinear models, and whether all three compartments are really necessary.

Animals↗
PubMed1997

Design of a general clinical notification system based on the publish-subscribe paradigm.

We describe the design and initial implementation of a notification sub-system, as a component of a modern information management architecture. The system, based on the publish-subscribe paradigm, provides a framework of event-based communications for the implementation of various important clinical applications including the notification of alerts and reminders with escalation algorithms, the reliable distribution of documents, and the implementation of intelligent patient-specific monitoring processes. The initial implementation of the system, providing the notification of the unit staff about new orders, indicates that the model is viable both in terms of functionality and ability to scale up.

Algorithms↗
PubMed1996

A comparison of six deconvolution techniques.

We present results for the comparison of six deconvolution techniques. The methods we consider are based on Fourier transforms, system identification, constrained optimization, the use of cubic spline basis functions, maximum entropy, and a genetic algorithm. We compare the performance of these techniques by applying them to simulated noisy data, in order to extract an input function when the unit impulse response is known. The simulated data are generated by convolving the known impulse response with each of five different input functions, and then adding noise of constant coefficient of variation. Each algorithm was tested on 500 data sets, and we define error measures in order to compare the performance of the different methods.

Algorithms↗
PubMed1990

Retina's eye view of the implant lens.

Using simple inexpensive equipment, still macro photographs were obtained of the ciliary body and lens capsule of donor eyes during the procedure of intraocular lens implantation. It is shown that implant lens loops, while correctly bag-implanted, can catch in the ciliary sulcus.

Ciliary Body↗
PubMed1988

In-the-bag posterior chamber lens implantation.

I designed a forceps for inserting intraocular lenses after cataract extraction and then studied the results of using this forceps in 122 cases. Seventy-eight percent of the IOLs were found to be successfully implanted in the capsular bag in 110 eyes examined up to 12 months after surgery. Visual acuity of 20/40 or better was achieved in 87% of patients. Postoperative complications were few and did not adversely affect visual acuity in the long term.

Cataract Extraction↗
PubMed1985

Family factors in the lives of drug users and abusers.

A review of the literature suggested nine family factors which had an impact upon drug use: parental absence, discipline, scapegoating, hypocritical morality, parent-child communication gap, parental divorce, mother-father conflicts, family breakup, and the use of "psychological crutches" to cope with stress. In addition, data were collected on the closest family member to the drug-taking subject, the subject's perception of the most powerful family member, the family member who used "psychological crutches," and situations where the most powerful person in the family used "psychological crutches." A paired analysis between drug users and drug abusers yielded significant differences on the use of two "psychological crutches" to cope with stressful situations: drugs and denial. Drug users were less likely to come from families where there was a communication gap and more likely to come from families which used democratic disciplinary techniques. Drug abusers came from families where there was a communication gap and either laissez faire or authoritarian discipline. Drug abusers also came from families where the person whom they defined as most powerful tended to use "psychological crutches" to cope with stress.

Adolescent↗
PubMedDate not supplied

Antiorthostatic suspension stimulates profiles of macrophage activation in mice.

The antiorthostatic suspension model simulates certain physiological effects of spaceflight. We have previously reported BDF1 mice suspended by the tail in the antiorthostatic orientation for 4 days express high levels of resistance to virulent Listeria monocytogenesinfection. In the present study, we examined whether the increased resistance to this organism correlates with profiles of macrophage activation, given the role of the macrophage in killing this pathogen in vivo. We infected BDF1 mice with a lethal dose of virulent L. monocytogenes on day 4 of antiorthostatic suspension and 24 h later constructed profiles of macrophage activation. Viable listeria could not be detected in mice suspended in the antiorthostatic orientation 24 h after infection. Flow cytometric analysis revealed the numbers of granulocytes and mononuclear phagocytes in the spleen of infected mice were not significantly altered as a result of antiorthostatic suspension. Splenocytes from antiorthostatically suspended infected mice produced increased titers of IL-1. Serum levels of neopterin, a nucleotide metabolite secreted by activated macrophages, were enhanced in mice infected during antiorthostatic suspension, but not in antiorthostatically suspended naive mice. Splenic macrophages from mice infected on day 4 of suspension produced enhanced levels of lysozyme. In contrast to the results from antiorthostatically suspended infected mice, macrophages from antiorthostatically suspended uninfected mice did not express enhanced bactericidal activities. The collective results indicate that antiorthostatic suspension can stimulate profiles of macrophage activation which correlate with increased resistance to infection by certain classes of pathogenic bacteria.

Aerospace Medicine↗